OK the problem is when i want to start windows whit 4gb memory instaled it does not start just black screen but whit 3gb of mem its all good.

Hi Doomtrain, welcome to the PCHF

Does windows completely not load?
It might be faulty memory.
I've been running 4gb memory for over 2 years now, and i know people who use 8gb perfectly fine.

It might also be a limitation of the motherboard

Thanks for a quick reply

Yes its just black screen and it stops.
Another thing is when i try to (on3gb mem) get voltage for memory on 2.1 (recommended) i get the same thing and i get blue screen same happened on win xpx32 pro .

It's starting to sound like more and more a limitation, or a problem with your motherboard.
Do you know what model it is?

ASUSTeK Computer Inc.

well its this this was so pose to be product for some time you know quad suport and good overclocking and cooling but now i dont know, it costs so much for a motherboard and now problems ??

Ok, well your motherboard supports up to 8gb memory...
To be honest, it sounds like you've got a bad memory stick as that 4gb one.

Try swapping them around and see what happens.